The present invention relates to an electronic material composition comprising a specific resin component, to electronic components to be manufactured from the employment of such an electronic material composition, and to the using method of such an electronic material composition.
Curable resins such as epoxy resin are employed as an important component in an electronic material composition which may or may not be mixed with a powdery electronic material such as ferrite powder or metallic powder in the employment thereof. Such electronic materials comprising a curable resin or a powdery electronic material are extensively employed mainly as a material for the manufacture of electronic components, e.g. as a molding material, a coating material, an electrode material, a bonding material, etc.
More specifically, the electronic materials can be employed as an electronic material for the following end-uses (1) to (5).
(1) As for the usage as a molding material of the electronic materials, they can be employed as a material on the occasion of manufacturing the core of wound chip coil for instance. In this case, ferrite powder is granulated together with a resin component and other components as required to obtain granules, which are then dry-molded into a rod like configuration and subjected to a curing treatment. The cured body thus obtained is then subjected to a cutting work to obtain a core whose both ends are provided with a flange. The same procedure can be also applied to the manufacture of the spool of air-core coil though the procedure involves no cutting work in this case. There is also known a so-called working-less manufacturing method wherein ferrite powder is wet-mixed with a resin component and a solvent to obtain a composition which is then molded by means of injection molding for instance to form a molded body, the molded body being subsequently cured.
(2) As for the usage of the electronic material as a coating material, there are four cases (a) to (d) as set forth below.
(a) The electronic material can be employed as an outer packaging material in such a manner that after a winding is applied to the aforementioned core, the resultant coil is coated with the electronic material.
(b) The electronic material can be employed as an electromagnetic shielding material covering the surface of a casing housing an electronic component. In this case, magnetic material powder is mixed with a resin component to obtain a mixture which is then molded into a sheet, a plurality of which are then simply adhered to each other so as to cover the surface of the casing. There is also known a case wherein the casing itself is constituted by a molded body molded from a mixture comprising metallic powder and a resin component.
(c) The electronic material can be employed as a covering material for a connecting cable of a digital video camera, a personal computer, a printer, etc. In this case, a resin component is turned into a molten state and then, extruded together with the cable.
(d) The electronic material can be employed as a covering material for covering the entire surface, including an electronic component, of a printed wiring board having an electronic component mounted thereon.
(3) As for the usage as an electrode material of the electronic materials, they can be employed as a conductive paste containing a glass frit and silver powder for instance, the paste being coated and then, baked to form an external terminal electrode of a chip component. There is also known a case wherein a conductive paste obtained through the mixing of conductive powder with a resin component and a solvent is coated on a chip component and then, baked to form an external terminal electrode likewise.
(4) As for the usage of the electronic material as a bonding material, there are two cases (a) and (b) as set forth below.
(a) The electronic material can be employed as a solder for soldering a chip component for example onto the soldering land of a printed wiring board.
(b) As in the case of manufacturing an LC laminated composite electronic component for instance, the electronic material can be employed as an adhesive material, i.e. as an interconnecting sheet in bonding different kinds of sheets with each other, for instance in a process wherein a green sheet laminate consisting of the same kind of material is laminated with another green sheet laminate consisting of the same kind of another material differing from the first mentioned material to form a composite laminate body, which is then baked to form an LC element. Namely, in this case, these green sheets can be formed of an electronic material composition wherein ferrite powder or dielectric material powder is wet-mixed with a resin and a solvent.
(5) As for the usage as a filler of the electronic materials, they can be employed for filling a joint portion in a situation wherein the wall of building is to be formed by joining electromagnetic shielding boards, panels or tiles to each other.
In relative to the aforementioned end-use (1), there is an increasing demand for the miniaturization of core in accordance with the recent trend to further miniaturize an electronic component. However, as the core becomes smaller, the rigid and fragile nature of the ferrite material becomes more prominent, thus making it difficult to exercise a fine working of the core. As a result, an off-specification product tends to generate, thus deteriorating the yield of the core. In the case of the core which is injection-molded using an electronic material composition prepared through a wet-mixing also, the toughness of core is insufficient. From a reflow soldering test wherein these worked or molded products are subjected to a thermal stress in the soldering step, these worked product as well as molded product are found accompanied with a problem in terms of strength.
In relative to the aforementioned end-use (2)(a), the conventional outer packaging material is accompanied with a problem in the mounting operation of so-called bulk component wherein individual component is picked up by means of an adsorption nozzle from an aggregate consisting of a large number of chips of the same kind and transferred so as to mount it at a predetermined region of a printed wiring board, because the outer packaging material is so rigid and hardly deformable that a gap tends to be generated between the adsorption nozzle and the surface portion of the outer packaging material being adsorbed, thus making it difficult for the adsorption nozzle to pick up the individual component due to slipping between them. Namely, a problem of mis-mount tends to be raised in picking up individual chip component from a large number of chips of the same kind. With a view to minimize this mis-mount, there has been conventionally proposed to improve the accuracy in configuration of the component. However, such a countermeasure is limited in terms of yield.
In relative to the aforementioned end-use (2)(b), when the configuration of casing includes a complicatedly deformed portion such as a complicatedly bent portion or a fine recessed and projected portion, it is difficult to closely adhere electromagnetic shielding sheets onto the wall of the casing. As a result, a sufficient electromagnetic shielding effect may not be ensured.
In relative to the aforementioned end-use (2)(a) and (2)(b), due to a thermal stress resulting from a difference in linear expansion coefficient between the coating material and the surface to be coated, the adhesion plane may be peeled off or a damage such as cracking may be generated in the coating material.
In relative to the aforementioned end-use (2)(c), since the coating material is formed of a resin material, the electromagnetic wave generated from the current flowing through the conductive wire of cable is allowed to radiate into the ambient atmosphere. As a result, the electronic instruments disposed around the cable would be badly affected by the electromagnetic wave, so that it is impossible to suppress so-called radiant noise which may become a cause for the malfunction of the electronic instruments. With a view to overcome this problem, there has been conventionally proposed a cable which is covered with a coating material formed of a magnetic material composition containing, as a resin component, acrylic-modified polyester resin. However, as for the cable which is an ordinary covered conductor not having such a countermeasure, there is no other way but to use as it is, so that such an ordinary cable, including the cable which has been already wired, is still accompanied with a problem that it is impossible to suppress the aforementioned radiant noise.
In relative to the aforementioned end-use (3), the electrode which is formed through the baking of a mixture comprising powdery silver and glass frit is employed on the occasion of soldering an electronic component to the soldering land of a printed wiring board. However, since the linear expansion coefficient of the electrode differs from that of the soldering land, a stress tends to generate between them due to changes in temperature. As a result, the electronic component is badly affected by such a stress, thereby deteriorating the durability of the electronic component in terms of keeping a predetermined performance thereof. The same problem as mentioned above is also applicable to the electrode which is formed through the baking of a mixture comprising powdery conductive material and a resin component. Because, since epoxy resin is employed as the resin component, the aforementioned thermal stress cannot be alleviated.
In relative to the aforementioned end-use (4)(a), since the solder to be employed for bonding the external terminal electrode of electronic component to the soldering land is so rigid and hardly deformable that it is impossible to alleviate the stress to be generated, due to changes in temperature, between the electrode and the soldering land as in the case of the aforementioned end-use (3), the electronic component would be badly affected by the stress, thereby deteriorating the durability of the electronic component. Therefore, if the problem pointed out in the aforementioned end-use (3) happens to occur simultaneously with this phenomenon, the durability of the electronic component would be further deteriorated.
In relative to the aforementioned end-use (4)(b), since, for example, a ferrite green sheet laminate constituting a composite laminate body differs in shrinkage factor from a dielectric material green sheet laminate also constituting the composite laminate body, cracks may be more likely to be generated on the occasion of baking the composite laminate body. Even if a baked body which is free from cracks can be obtained, since the composite laminate body is constituted by different kinds of green sheet laminates differing in linear expansion coefficient, cracks may be more likely to be generated in the baked body when the baked body is left under the conditions where the temperature thereof is caused to change, especially when the baked body is repeatedly left under such conditions.
In relative to the aforementioned end-use (5), although a silicone resin is generally employed as a filler, it is impossible to prevent an electromagnetic wave from entering into a building from the outside thereof through the filler containing the silicon resin, and at the same time, an electromagnetic wave generated form electronic instruments such as a personal computer employed inside the building is allowed to leak to the outside of the building through the resin-filled portions between electromagnetic shielding boards, panels or tiles, thereby raising a problem of the leakage of information via this leaked electromagnetic wave.
Therefore, a fist object of this invention is to provide an electronic material composition which enables to obtain a molded body having a sufficient strength even if the molded body is miniaturized, being suited for improving the yield, and being resistive to a sharp change of temperature, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A second object of this invention is to provide an electronic material composition to be employed for manufacturing an external packaging material which is capable of withstanding a stress that may be generated under a thermal load on the occasion of reflow soldering or on the occasion of heat cycle test, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A third object of this invention is to provide an electronic material composition to be employed for manufacturing an external packaging material having a sufficient flexibility enabling to obtain a bulk component which can be easily adsorbed by an adsorption nozzle of a mounter, and exhibiting an excellent resistivity to a thermal stress that may be generated due to a difference in linear expansion coefficient between the external packaging material and a body to be packaged, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A fourth object of this invention is to provide an electronic material composition to be employed for manufacturing a covering material having a sufficient flexibility enabling to cover a casing having a complicated surface configuration in conformity with the complicated surface configuration so as to ensure a sufficient electromagnetic shielding, and exhibiting an excellent resistivity to a thermal stress that may be generated due to a difference in linear expansion coefficient between the covering material and a body to be covered, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A fifth object of this invention is to provide an electronic material composition to be employed for manufacturing a covering material or a casing material, which is capable of preventing the generation of radiant noise, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A sixth object of this invention is to provide an electronic material composition to be employed for forming an external electrode for electronic component, which is capable of alleviating a stress resulting from changes in temperature of the electronic component even if the stress is generated in an electronic component mounted on a printed wiring board, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A seventh object of this invention is to provide an electronic material composition to be employed for bonding an electronic component to a printed wiring board, which is capable of alleviating a stress even if the stress is generated in the electronic component from changes in temperature thereof, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
An eighth object of this invention is to provide an electronic material composition to be employed for manufacturing a bonding material which enables to obtain a bonded body of a couple of members, which is capable of absorbing a difference, if any, in irreversible expansion coefficient or shrinkage factor between these member due to the heat-treatment, thereby making it possible to prevent the generation of cracks in the bonded body, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A ninth object of this invention is to provide an electronic material composition which is capable of withstanding a thermal stress under a condition where temperature is differentiated, even if the electronic material composition is employed as a bonding material for bonding a plurality of members each having a different linear expansion coefficient from each other, or as a covering material for covering a plurality of members each having a different linear expansion coefficient, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A tenth object of this invention is to provide an electronic material composition which enables to obtain a filler to be employed for manufacturing an electromagnetic shielding wall which is capable of preventing an electromagnetic wave from entering or leaking through a gap between the electromagnetic shielding boards, panels or tiles of building, to provide an electronic component formed of such an electronic material composition, and to provide the use of such an electronic material composition.
A eleventh object of this invention is to provide the use of an electronic material composition which enables to prevent an object from being damaged which may be caused due to the heating for curing, and to provide an electronic component to be obtained from the use of such an electronic material composition.
With a view to solve the aforementioned problems, this invention provides (1) an electronic material composition comprising at least a curable polymer and exhibiting the following physical properties (a) and (b) after being cured to form a cured body;
(a) temperature characteristic in relative to stiffness modulus, which is featured in that a glass transition temperature in a process of shifting the cured body from a glassy state to a rubbery state due to the change of stiffness modulus in relative to temperature is in the range of xe2x88x9250 to 50xc2x0 C.; and
(b) stiffness modulus in said rubbery state which is in the range of 105 Pa to 107 Pa.
This invention further provides (2) an electronic material composition comprising at least a curable polymer and exhibiting the following physical properties (a), (b) and (c) after being cured to form a cured body;
(a) temperature characteristic in relative to stiffness modulus, which is featured in that a glass transition temperature in a process of shifting the cured body from a glassy state to a rubbery state due to the change of stiffness modulus in relative to temperature is in the range of xe2x88x9250 to 50xc2x0 C.;
(b) stiffness modulus in said rubbery state which is in the range of 105 Pa to 107 Pa; and
(c) extensibility which cannot be destroyed even if said cured body is subjected to a shear deformation of 5% at a temperature of xe2x88x9250xc2x0 C.
This invention further provides (3) an electronic material composition comprising at least powdery electronic material and a curable polymer, and exhibiting the following physical properties (d) and (e) after being cured to form a cured body;
(d) temperature characteristic in relative to stiffness modulus, which is featured in that a glass transition temperature in a process of shifting the cured body from a glassy state to a rubbery state due to the change of stiffness modulus in relative to temperature is in the range of xe2x88x9250 to 50xc2x0 C.; and
(e) stiffness modulus in said rubbery state which is in the range of 106 Pa to 108 Pa.
This invention further provides (4) an electronic material composition comprising at least powdery electronic material and a curable polymer, and exhibiting the following physical properties (d), (e) and (f) after being cured to form a cured body;
(d) temperature characteristic in relative to stiffness modulus, which is featured in that a glass transition temperature in a process of shifting the cured body from a glassy state to a rubbery state due to the change of stiffness modulus in relative to temperature is in the range of xe2x88x9250 to 50xc2x0 C.;
(e) stiffness modulus in said rubbery state which is in the range of 106 Pa to 108 Pa; and
(f) extensibility which cannot be destroyed even if said cured body is subjected to a shear deformation of 2% at a temperature of xe2x88x9250xc2x0 C.
This invention further provides (5) an electronic material composition according to any one of the aforementioned items (1) to (4), wherein the curable polymer comprises polysulfide-based polymer containing therein polysulfide rubber skeleton (xe2x80x94Sxe2x80x94Sxe2x80x94).
This invention further provides (6) an electronic material composition according to the aforementioned item (5), wherein the polysulfide-based polymer is polysulfide.
This invention further provides (7) an electronic material composition according to the aforementioned item (5), wherein the polysulfide-based polymer is polysulfide-modified epoxy polymer which is a reaction product between polysulfide and an epoxy compound.
This invention further provides (8) an electronic material composition according to any one of the aforementioned items (1) to (4), wherein the electronic material composition is adapted for use for forming an electronic component and formulated into a raw material for forming a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body.
This invention further provides (9) an electronic material composition according to any one of the aforementioned item (5), wherein the electronic material composition is adapted for use for forming an electronic component and formulated into a raw material for forming a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body.
This invention further provides (10) an electronic material composition according to any one of the aforementioned item (6), wherein the electronic material composition is adapted for use for forming an electronic component and formulated into a raw material for forming a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body.
This invention further provides (11) an electronic material composition according to any one of the aforementioned item (7), wherein the electronic material composition is adapted for use for forming an electronic component and formulated into a raw material for forming a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body.
This invention further provides (12) an electronic component comprising a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body as set forth in the aforementioned item (8).
This invention further provides (13) an electronic component according to the aforementioned item (12), wherein the molded body is a core of wound chip coil which can be obtained by means of molding, and the electronic component is a wound chip coil having said core.
This invention further provides (14) an electronic component according to the aforementioned item (12), wherein the covering body is an external packaging covering the winding of wound chip coil, and the electronic component is a wound chip coil having said external packaging.
This invention further provides (15) an electronic component according to the aforementioned item (12), wherein the covering body is an electromagnetic shielding covering body for a casing, and the electronic component is a casing for an electromagnetic component having said electromagnetic shielding covering body.
This invention further provides (16) an electronic component according to the aforementioned item (12), wherein the covering body is a cable sheath for preventing radiant noise, and the electronic component is a radiant noise-free cable having said cable sheath for preventing radiant noise.
This invention further provides (17) an electronic component according to the aforementioned item (12), wherein the covering body is an external packaging body for packaging mounted components on a printed wiring board, and the electronic component is a printed wiring board having said external packaging.
This invention further provides (18) an electronic component according to the aforementioned item (12), wherein the packed body is obtained by making use of an electromagnetic shielding caulking material as a filler for filling a gap between the electromagnetic shielding boards, panels or tiles, which are designed to form an electromagnetic shielding wall, and the electronic component is an electromagnetic shielding wall having said packed body.
This invention further provides (19) an electronic component according to the aforementioned item (12), wherein the electrode is an external electrode of a chip type electronic component, and the electronic component is a chip type electronic component having said electrode.
This invention further provides (20) an electronic component according to the aforementioned item (12), wherein the joining body is a conductive connecting body for connecting an external electrode of chip component with a soldering land of a printed wiring board, and the electronic component is a printed wiring board having said conductive connecting body.
This invention further provides (21) an electronic component according to the aforementioned item (12), wherein the joining body is an interface connecting body for connecting a pair of members with each other through the interface thereof, each member exhibiting a different irreversible expansion coefficient or shrinkage factor from the other as they are heat-treated, and the electronic component is a composite electronic component wherein said members are connected with each other via said interface connecting body and heat-treated.
This invention further provides (22) an electronic component according to the aforementioned item (12), wherein the joining body is designed to connect a plurality of members, each member exhibiting a different linear expansion coefficient from one another, and the electronic component is an electronic component having said plurality of members which are connected through said joining body.
This invention further provides (23) an electronic component comprising a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body as set forth in the aforementioned item (10).
This invention further provides (24) an electronic component according to the aforementioned item (23), wherein the molded body is a core of wound chip coil which can be obtained by means of molding, and the electronic component is a wound chip coil having said core.
This invention further provides (25) an electronic component according to the aforementioned item (23), wherein the covering body is an external packaging covering the winding of wound chip coil, and the electronic component is a wound chip coil having said external packaging.
This invention further provides (26) an electronic component according to the aforementioned item (23), wherein the covering body is an electromagnetic shielding covering body for a casing, and the electronic component is a casing for an electromagnetic component having said electromagnetic shielding covering body.
This invention further provides (27) an electronic component according to the aforementioned item (23), wherein the covering body is a cable sheath for preventing radiant noise, and the electronic component is a radiant noise-free cable having said cable sheath for preventing radiant noise.
This invention further provides (28) an electronic component according to the aforementioned item (23), wherein the covering body is an external packaging body for packaging mounted components on a printed wiring board, and the electronic component is a printed wiring board having said external packaging.
This invention further provides (29) an electronic component according to the aforementioned item (23), wherein the packed body is obtained by making use of an electromagnetic shielding caulking material as a filler for filling a gap between the electromagnetic shielding boards, panels or tiles, which are designed to form an electromagnetic shielding wall, and the electronic component is an electromagnetic shielding wall having said packed body.
This invention further provides (30) an electronic component according to the aforementioned item (23), wherein the electrode is an external electrode of a chip type electronic component, and the electronic component is a chip type electronic component having said electrode.
This invention further provides (31) an electronic component according to the aforementioned item (23), wherein the joining body is a conductive connecting body for connecting an external electrode of chip component with a soldering land of a printed wiring board, and the electronic component is a printed wiring board having said conductive connecting body.
This invention further provides (32) an electronic component according to the aforementioned item (23), wherein the joining body is an interface connecting body for connecting a pair of members with each other through the interface thereof, each member exhibiting a different irreversible expansion coefficient or shrinkage factor from the other as they are heat-treated, and the electronic component is a composite electronic component wherein said members are connected with each other via said interface connecting body and heat-treated.
This invention further provides (33) an electronic component according to the aforementioned item (23), wherein the joining body is designed to connect a plurality of members, each member exhibiting a different linear expansion coefficient from one another, and the electronic component is an electronic component having said plurality of members which are connected through said joining body.
This invention further provides (34) an electronic component comprising a body selected from the group consisting of a molded body, a packed body, a covering body, an electrode and a joining body as set forth in the aforementioned item (11).
This invention further provides (35) an electronic component according to the aforementioned item (34), wherein the molded body is a core of wound chip coil which can be obtained by means of molding, and the electronic component is a wound chip coil having said core.
This invention further provides (36) an electronic component according to the aforementioned item (34), wherein the covering body is an external packaging covering the winding of wound chip coil, and the electronic component is a wound chip coil having said external packaging.
This invention further provides (37) an electronic component according to the aforementioned item (34), wherein the covering body is an electromagnetic shielding covering body for a casing, and the electronic component is a casing for an electromagnetic component having said electromagnetic shielding covering body.
This invention further provides (38) an electronic component according to the aforementioned item (34), wherein the covering body is a cable sheath for preventing radiant noise, and the electronic component is a radiant noise-free cable having said cable sheath for preventing radiant noise.
This invention further provides (39) an electronic component according to the aforementioned item (34), wherein the covering body is an external packaging body for packaging mounted components on a printed wiring board, and the electronic component is a printed wiring board having said external packaging.
This invention further provides (40) an electronic component according to the aforementioned item (34), wherein the packed body is obtained by making use of an electromagnetic shielding caulking material as a filler for filling a gap between the electromagnetic shielding boards, panels or tiles, which are designed to form an electromagnetic shielding wall, and the electronic component is an electromagnetic shielding wall having said packed body.
This invention further provides (41) an electronic component according to the aforementioned item (34), wherein the electrode is an external electrode of a chip type electronic component, and the electronic component is a chip type electronic component having said electrode.
This invention further provides (42) an electronic component according to the aforementioned item (34), wherein the joining body is a conductive connecting body for connecting an external electrode of chip component with a soldering land of a printed wiring board, and the electronic component is a printed wiring board having said conductive connecting body.
This invention further provides (43) an electronic component according to the aforementioned item (34), wherein the joining body is an interface connecting body for connecting a pair of members with each other through the interface thereof, each member exhibiting a different irreversible expansion coefficient or shrinkage factor from the other as they are heat-treated, and the electronic component is a composite electronic component wherein said members are connected with each other via said interface connecting body and heat-treated.
This invention further provides (44) an electronic component according to the aforementioned item (34), wherein the joining body is designed to connect a plurality of members, each member exhibiting a different linear expansion coefficient from one another, and the electronic component is an electronic component having said plurality of members which are connected through said joining body.
This invention further provides (45) a method of using an electronic material composition, which comprises the steps of; forming an electronic component having a semi-cured state of a molded body, a packed body, a covering body, an electrode or a joining body by making use of the electronic material composition of any one of the aforementioned items (1) to (4); and completely curing the molded body, the packed body, the covering body, the electrode or the joining body to obtain the electronic component having a cured state of the molded body, the packed body, the covering body, the electrode or the joining body.
This invention further provides (46) a method of using an electronic material composition, which comprises the steps of; forming an electronic component having a semi-cured state of a molded body, a packed body, a covering body, an electrode or a joining body by making use of the electronic material composition of the aforementioned item (6); and completely curing the molded body, the packed body, the covering body, the electrode or the joining body to obtain the electronic component having a cured state of the molded body, the packed body, the covering body, the electrode or the joining body.
This invention further provides (47) a method of using an electronic material composition, which comprises the steps of; forming an electronic component having a semi-cured state of a molded body, a packed body, a covering body, an electrode or a joining body by making use of the electronic material composition of the aforementioned item (7): and completely curing the molded body, the packed body, the covering body, the electrode or the joining body to obtain the electronic component having a cured state of the molded body, the packed body, the covering body, the electrode or the joining body.
The electronic material composition according to this invention may be either a mixture comprising a resin component, to which powdery electronic materials such as powdery ferrite, powdery electric conductor and a functional filler such as a powdery filler are mixed together, or a mixture comprising a resin component, to which such powdery electronic materials are not mixed together. The former mixture can be employed, by optionally selecting a suitable kind of powdery electronic materials, as a coating material, a molding material, an electrode material, a joining material or a filler. Even in the case of the latter mixture, it may be employed as any of the aforementioned materials, for example as a packaging material for a wound chip coil. In any case, it is desirable that these resinous material compositions have the following physical properties.
First of all, in the case of the resinous material composition containing no powdery electronic material, the cured product thereof should desirably be provided with the following features (a) and (b).
(a) Temperature characteristic in relative to stiffness modulus, which is featured in that a glass transition temperature in a process of shifting the cured body from a glassy state to a rubbery state due to the change of stiffness modulus in relative to temperature is in the range of xe2x88x9250 to 50xc2x0 C.; and
(b) stiffness modulus in said rubbery state which is in the range of 105 Pa to 107 Pa.
With respect to the stiffness modulus in relative to temperature, the rate of change thereof is relatively large especially in the process of being shifted from a glassy state to a rubbery state. Therefore, due to this large rate of change, it can be distinguished from the glassy state or the rubbery state where the rate of change is relatively small. The glass transition temperature is located within the range of temperature which corresponds to the variation curve exhibiting a large rate of change and can be represented by Tg.
In terms of dynamic viscoelasticity, the storage elastic modulus (Gxe2x80x2) representing the magnitude of the elasticity characteristics of polymer generally decreases as the temperature increases. In the case, while the Gxe2x80x2 of thermoplastic resin continues to decrease even in the rubber region thereof, the Gxe2x80x2 of cross-linking type polymer keeps to remain the same level or increases in the rubber region thereof without further decreasing. On the other hand, the relationship between temperature and the dynamic loss modulus (Gxe2x80x3) representing the magnitude of viscosity characteristics of polymer can be shown by a curve having a maximal point. Further, dynamic loss (loss tangent) tan xcex4 (xcex4 is a phase angle (a phase difference between stress and strain vector)) can be measured from a phase difference between stress and the simple harmonic oscillation of strain, thereby making it possible to assume the dynamic loss as a scale indicating the degree of loss, due to the generation of heat, of dynamic energy received by the system. However, the temperature indicating the peak value of tan xcex4 in the curve Gxe2x80x3 would become Tg (glass transition temperature) of dynamic measurement, this peak value may be assumed as the aforementioned glass transition temperature Tg. This Tg value can be made higher by increasing the crosslinking density or by designing a polymer which is high in nuclear structural concentration such as phenyl nucleus. This Tg value can be also made lower by loosening the crosslinking density, by introducing an alkyl chain of fatty acid into the polymer, or by mixing a plasticizer into the polymer. The details on these matters can be found in a document xe2x80x9cThe Latest Pigment Dispersion Technologyxe2x80x9d, 1993, Technological Information Association, pp 53-54, para 2.1, which is incorporated herein for reference.
With regard to the aforementioned features (a) and (b), in the case of the cured product of epoxy resin that has been conventionally employed in the fields of electronic material, the Tg thereof is generally higher than 50xc2x0 C. and the stiffness modulus in the rubbery state is also higher than 108Pa. On the other hand, the ordinary crosslinked rubber exhibiting a large elasticity is generally extremely low in Tg, i.e. not less than twice lower than xe2x88x9250xc2x0 C. Whereas this invention is featured in the employment of an electronic material having the aforementioned features of not only (a) but also (b), which features are not found in the conventional electronic material. As a result, it is possible according to this invention to provide an electronic material excellent in flexibility, toughness and resistivity to thermal stress. By the way, the resin component to be employed in this invention is curable and hence can be distinguished from thermoplastic resin. If the value of Tg is too large, the toughness of the electronic material as it is placed under a condition where there is a prominent difference in temperature as in the case of the aforementioned reflow soldering test would be badly deteriorated. On the other hand, if the value of Tg is too small, the density of crosslinking would become low and hence become poor in heat resistance. Further, if the stiffness modulus is too large, the relaxation of thermal stress or mechanical stress would be badly deteriorated, while if the stiffness modulus is too small, the shape retention would be deteriorated.
As explained above, the resinous material composition to be employed in this invention can be distinguished from other conventional resinous material compositions in the respect that it is provided with the aforementioned features (a) and (b). It is also possible to further distinguish the resinous material composition of this invention from the conventional ones by further providing it with the following feature (c).
(c) Extensibility which cannot be destroyed even if a cured body is subjected to a shear deformation of 5% at a temperature of xe2x88x9250xc2x0 C.
This feature (c) illustrates the absorbency of external force, which enables to absorb an external force without giving rise to the fracture of cured product. In the case of the cured product of epoxy resin that has been conventionally employed in the fields of electronic material, a fracture is caused to occur as the cured product is subjected to a shear deformation of 5% at a temperature of xe2x88x9250xc2x0 C. Therefore, the conventional cured product of epoxy resin can be much more distinguished from the resinous material composition of this invention in this feature (c) rather than the aforementioned feature (b).
As for the resinous material composition which meets the aforementioned various characteristics, a resinous material composition comprising, as a main component, polysulfide-based polymer can be exemplified. It is of course possible to employ other kinds of resinous material composition.
This polysulfide-based polymer may be a polymer having a polysulfide rubber skeleton (xe2x80x94Sxe2x80x94Sxe2x80x94) in its molecule, a polymer comprising, as a main component, polysulfide having a large number of sulfide groups, or a polysulfide polymer itself. This polysulfide can be represented by the general formula, HSxe2x80x94( . . . xe2x80x94SS)n . . . xe2x80x94SH (wherein xe2x80x9c. . .xe2x80x9d is an organic group having a skeleton comprising a sulfide bond, a carbon-carbon bond, an ether bond, etc.; and n is an integer including zero), and is capable of bringing about a dehydration reaction in the presence of oxygen as shown below, the dehydration reaction taking place at the terminal portion of each polysulfide molecule for instance. Further, in the presence of oxidizer, the polysulfide may be formulated into a cold-setting polymer.
. . . xe2x80x94SH+HSxe2x80x94. . . +0xe2x86x92. . . xe2x80x94SSxe2x80x94. . .
As for the molecule of polysulfide, the following molecule can be exemplified specifically.
HSxe2x80x94C2H4OCH2OC2H4xe2x80x94SSxe2x80x94C2H4OCH2OC2H4xe2x80x94SH
This specific compound is known and employed as a component for a caulking material for building, and some kinds of this compound is placed on the market.
This polysulfide-based polymer may be a reaction product between polysulfide and a component of other kind of polymer or compound, or may be made curable by introducing epoxy group or other kinds of reactive functional group.
As for polysulfide modified epoxy resin consisting of a polysulfide modified epoxy polymer which is a reaction product between the aforementioned polysulfide and an epoxy compound, a resin consisting of a polymer to be obtained through a reaction between thiol group (xe2x80x94SH) and epoxy group can be exemplified. For example, a resin consisting of a straight-chain high-molecular weight compound to be obtained from the reaction shown in the following general formula (1) for instance and having a weight average molecular weight of 1000 to 22000 can be exemplified. It is also possible to exemplify a resin consisting of a straight-chain high-molecular weight compound comprising, as a fundamental skeleton, a reaction product to be obtained from the reaction shown in the following general formula (1), polysulfide polymer attached to epoxy groups formed respectively at both ends of the skeleton, and epoxy polymer attached to the terminal thiol group of the polysulfide polymer, said straight-chain high-molecular weight compound having a weight average molecular weight of 1000 to 22000, wherein the equivalent ratio formulated of the polymer components is adjusted such that the terminal group of said straight-chain high-molecular weight compound to be ultimately formed through the repetition of the polymerization thereof is constituted by epoxy group. 
(wherein R represents a residual group to be derived by removing both terminal groups from polysulfide polymer, i.e. xe2x80x94(C2H4xe2x80x94Oxe2x80x94CH2xe2x80x94Oxe2x80x94C2H4xe2x80x94Sxe2x80x94S)nxe2x80x94C2H4xe2x80x94Oxe2x80x94CH2xe2x80x94Oxe2x80x94C2H4xe2x80x94; and Rxe2x80x2 is C6H4xe2x80x94CH2xe2x80x94C6H4xe2x80x94 (wherein C6H4is benzene ring)
The reaction components and the extensibility of product are schematically shown in FIG. 1 (R and Rxe2x80x2 of the general formula 1 are also shown therein).
Specific examples of epoxy compound useful in this case are bisphenol type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin (both, Dai-Nippon Ink Chemical Industries Co., Ltd.), Eposet (BPA328) and Eposet (BPF307) (both, Nihon Shokubai Co., Ltd.).
Not only the aforementioned reaction product having epoxy group on both ends, but also a resin consisting of polysulfide-modified epoxy polymer having epoxy group at one end of the polymer as well as other portion of polymer can be cured by using them together with a curing agent. Whereas when a latent curing agent (a curing agent which is hardly capable of functioning as a curing agent at ordinary temperature but is capable of functioning as a curing agent upon heating) is employed together with these polymers, a molded product or coated film consisting of a cured resin can be obtained while maintaining the same workability as the ordinary coating material.
Polysulfides such as polysulfide polymer, epoxy compounds, the aforementioned polysulfide-modified epoxy polymer and other polysulfide-modified curable polymer where a reactive compound other than epoxy compound is employed can be formed, singly or in combination of two or more kinds, into a curable resin composition for electronic materials together with, if required, at least one kind of additive selected from the group consisting of other kinds of curable polymer, non-curable polymers including rubber, curing agents such as latent curing agents, fillers and coupling agents. The curable resin composition thus formulated can be employed for obtaining a cured molded product or coated film. It is possible, in this case also, to combine a greatly extensible skeleton with a slightly extensible skeleton as shown in FIG. 1.
As for the curing agent, it is possible to employ imidazole type amine adducts, straight chain type dicarbohydrazide, etc. Specific examples of the curing agent include PNxe2x80x94H and MYxe2x80x94H (trademark, Ajinomoto Co., Ltd.).
The cured film containing as a main component the aforementioned polysulfide-based polymer exhibits a Tg value which is the same with or lower than that of the cured film of silicone resin which is known as being excellent in flexibility, and also exhibits the same degree or a lower degree of relaxation to thermal stress when it is employed as a joining material or as an electrode material as compared with the known cured film of silicone resin. Even in the comparison with the cured film of epoxy resin, the cured film containing as a main component the aforementioned polysulfide-based polymer is comparable thereto or more excellent in terms of solvent resistance, chemical resistance and heat resistance of the adhesive power thereof to a metal, etc. For instance, the cured film containing as a main component the aforementioned polysulfide-based polymer is allowed to be barely oxidized when it is heated to a temperature higher than 230xc2x0 C.
As compared with silicone resin, the curing of the resinous material composition containing the aforementioned polysulfide can be more easily controlled by adjusting the quantity of oxygen to be supplied. Further, the degree of curing of polysulfide-based polymer having epoxy group introduced therein can be also easily controlled, so that the polymer in the B-stage thereof, i.e. in a semi-cured state thereof (irrespective of whether or not the quantity of curing is larger or smaller than a half thereof) can be employed for covering or filling an object in conformity with the specific configuration of the object. Thus, even if the object has an odd-shaped portion, the polymer can be applied and then completely cured so as to conform with the shape of the object.
As explained above, the resinous material composition containing the aforementioned polysulfide is provided with features which are comparable to those of the silicone resin and epoxy resin, and is also excellent in adaptability in the use thereof. Further, this resinous material composition can be employed together with these silicone resin and epoxy resin, thereby allowing the polysulfide or other kinds of polysulfide-based polymer to be reacted with the polymers of these resins. Alternatively, in addition to the co-use thereof together with silicone resin and/or epoxy resin, this resinous material composition can be employed together with other components so as to obtain a material satisfying the aforementioned physical features (a) and (b), or (a) to (c).
The aforementioned polysulfide-based polymer or a mixture thereof with other kinds of polymer component may be formulated together with a solvent including an epoxy-containing reactive diluent or other non-reactive solvent, thereby enabling the resinous material composition per set to be used as an electronic material composition. Alternatively, the resinous material composition may be mixed with a powdery electronic material, the examples of which include a magnetic material such as powdery ferrite; a conductive powder such as metallic powder (such as silver powder and copper powder) and carbon powder; and a functional filler such as a packing material, thereby obtaining an electronic material composition such as a conductive material composition or a magnetic material composition.
If the aforementioned polysulfide-based polymer or a mixture thereof with other kinds of polymer component is to be employed as a mixture thereof with a powdery magnetic material, 0 to 60% by volume of the powdery magnetic material can be mixed with 40 to 100% by volume of the polysulfide-based polymer or a mixture thereof with other kinds of polymer component to obtain a magnetic material composition which may further contain, if required, other kinds of resin, a solvent or other kinds of additive. As for the powdery magnetic material, various kinds of ferrite power can be employed. On the other hand, if the aforementioned polysulfide-based polymer or a mixture thereof with other kinds of polymer component is to be employed as a mixture thereof with a powdery conductive material, 0 to 60% by volume of the powdery conductive material can be mixed with 40 to 100% by volume of the polysulfide-based polymer or a mixture thereof with other kinds of polymer component to obtain a conductive material composition which may further contain, if required, other kinds of resin, a solvent or other kinds of additive. As for the powdery conductive material, a metallic powder composed of silver, copper, aluminum, etc. or carbon black can be employed. It is also possible in this case to employ fullerene (C60 or C70 type carbon). By the way, the aforementioned expression of: xe2x80x9c0 to 60% by volumexe2x80x9d may be replaced by the expression of: xe2x80x9cnot more than 60% by volumexe2x80x9d. The same substitution of expression can be also applied to where the expression of xe2x80x9c0 to - - -xe2x80x9d is referred to hereinafter.
The physical properties of cured products of an electronic material composition including the aforementioned magnetic material composition, conductive material composition and other kinds of material compositions to be obtained in the same manner as those of the aforementioned magnetic or conductive material composition are required to have the following features.
(d) Temperature characteristic in relative to stiffness modulus, which is featured in that a glass transition temperature in a process of shifting the cured body from a glassy state to a rubbery state due to the change of stiffness modulus in relative to temperature is in the range of xe2x88x9250 to 50xc2x0 C.; and
(e) stiffness modulus in said rubbery state which is in the range of 106Pa to 108Pa.
As explained above, the resinous components to be employed in this invention can be distinguished from the conventional resinous material compositions employing other resinous components in the respect that it is provided with the aforementioned features (d) and (e). It is also possible to further distinguish the resinous material composition of this invention from the conventional ones by further providing it with the following feature (f).
(f) Extensibility which cannot be destroyed even if a cured body is subjected to a shear deformation of 2% at a temperature of xe2x88x9250xc2x0 C.
The meanings of terms as well as the functions of features related to these features (d) to (f) are the same as described with reference to the aforementioned features (a) to (c).
It is possible, through the employment of such an electronic material composition, to provide a material for electronic parts or electronic products, which is capable of exhibiting an excellent effect which the conventional materials have failed to provide.
For example, by adjusting the quantity of a curing agent to be employed so as to reduce the inter-crosslinking point density representing one of the physical properties of cured product, or by increasing the ratio of polysulfide rubber skeleton occupying the skeleton of polymer so as to adjust the entanglement of rubber molecule chain, the glass transition temperature can be lowered and at the same time, excellent breaking extension property can be ensured while retaining a low stiffness modulus. As a result, it is now possible to simultaneously realize not only the reduction of residual stress at the moment of curing a resin, but also the relaxation of stress that has been generated by heat load.
Specifically, if the aforementioned magnetic material composition is to be employed as a packaging material to be applied to the winding of a wound chip coil, it is possible to reduce the quantity of volatilization of solvent or to make solvent-free thereby making it possible to reconsider the drying step as a curing condition of resin and at the same time, the glass transition temperature representing one of the physical properties of curable resin can be lowered, or the residual stress to be generated prominently at a temperature of not higher than the glass transition temperature can be minimized, thereby making it possible to reduce the residual stress at the moment of initial curing as well as at the moment of cooling. Further, owing to the lowering of glass transition temperature, the reduction of stiffness modulus (the reduction of stress generated) and the improvement of elastic limit elongation percentage (the absorption of stress generated at a temperature of not higher than the glass transition temperature), it is now possible to reduce or absorb the stress generated at the moment of the repetition of heat load. As a result, the generation of peel-off of packing material from the core or of cracking of packing material can be inhibited.
The aforementioned solvent-free can be realized by making use of a reactive diluent such as an epoxy-containing solvent for instance. The lowering of glass transition temperature can be realized by reducing the crosslinking density and by increasing the entanglement of molecule by long molecular chains. For the purpose of lowering the stiffness modulus of the cured product in a state of glass, a modified silicone oil for instance may be co-used as a flexibilizer. By making use of these additives, the glass transition temperature can be lowered to not higher than the normal temperature (25xc2x0 C.), the breaking extension percentage can be increased to 5% or more (even if a powdery electronic material such as ferrite powder for instance is added at a ratio of 50% by volume), the composition can be made solvent-free, and the Young""s modulus of the cured product in a state of glass can be reduced to about a half of the current volume products.
As for the method of increasing the breaking extension percentage, the modification of physical properties of cured product may be performed making use of a main component. Specifically, it is preferable, for this purpose, to employ polysulfide-modified epoxy polymer that can be derived from a reaction between the aforementioned epoxy resin and polysulfide polymer.
When the core of wound chip coil is molded by means of injection molding by making use of the aforementioned magnetic material composition, it is possible to obtain the core which is excellent in reflow solderability and in toughness to shock, and to increase, in conformity with the flexibility of polymer, the filling quantity of ferrite which influences the electric property of the core. Therefore, it is possible to obtain the core without necessitating the cutting work or with so-called work-less, while enabling the degree of freedom in configuration to be realized, enabling the miniaturization of the core to be realized, and enabling the high-functionalization of the core to be realized without necessitating high precision and with high yield. As a result, it is possible to obtain a wound chip coil of high performance at low cost, which the prior art has failed to realize.
The absorption of stress due to a difference in thermal expansion coefficient of the resin for packaging as well as the improvement in shock resistance in conformity with an increase in fineness of chip can be realized as mentioned above by decreasing the elastic modulus of resin, by lowering the glass transition temperature, by increasing the elongation percentage, thereby lowering the residual stress and relaxing the stress thus generated.
Further, when the aforementioned magnetic material composition or resin material composition is employed as a packaging material for covering the winding wound around the core of wound chip coil, a portion of the packaging material of the wound chip coil, on which the adsorption nozzle of a mounter is designed to be adsorbed, is constituted by a flexible polymer component exhibiting a low elastic modulus, so that the packaging material is enabled to be deformed in conformity with the configuration of the contacting surface of adsorption nozzle, thereby scarcely allowing a gap to be formed therebetween. As a result, no slipage can be caused to generate between the nozzle and the packaging material, thus making it possible to minimize the failure of mounting. After the mounting of the chip coil, the packaging material is allowed to restore to the original configuration without inviting no disadvantage as far as the external configuration of the chip coil is concerned.
Further, when the aforementioned magnetic material composition or resin material composition is employed for covering the walls of casing, an electromagnetic shielding layer which is capable of shielding electromagnetic waves from outside which may give an influence to electronic parts mounted inside the casing and hence capable of preventing the generation of noise can be formed. In this case, when the magnetic material composition is formed into a gel-like or putty-like state by making use of a semi-cured polymer component as it is employed for coating the casing and subsequently cured, the workability thereof can be greatly improved as compared with the case where completely uncured polymer is made use of. Irrespective of whether a semi-cured polymer is employed or a completely uncured polymer is employed, the magnetic material composition is formed at first into a sheet by casting it on a releasable film or by extrusion-molding it, and the resultant sheet is then adhered onto the casing (body to be covered with) under heating. In either cases, a troublesome operation of injection-molding an electromagnetic shielding sheet as in the case of the prior art can be omitted, and at the same time, since the polymer employed herein is low in elastic modulus and flexible, the magnetic material composition employing this Polymer can be employed to form an electromagnetic shielding sheet layer for the casing, which is capable of suitably conforming to an odd-shaped surface, of closely adhering to the casing, and of resisting repeated exposures to a difference in temperature of cold and hot.
Irrespective of whether this magnetic material composition is employed as a packaging material or as a covering material, this magnetic material composition is capable of exhibiting an excellent stress relaxation property against the thermal stress to be generated when these materials are placed under a condition where temperature is differentiated.
In the employment of the magnetic material composition as a covering material for the lead wire of cable, the magnetic material composition may be extrusion-molded together with the lead wire, or may be coated on the covering layer of the conventional cable or extrusion-molded together with the covering layer of the conventional cable. It is also possible in this case to provide a cable having a covering layer where the polymer component is low in elastic modulus and flexible, and which is capable preventing radiation noise.
In the employment of the magnetic material composition as an outer electrode material for electronic parts, a conductive material paste consisting of the magnetic material composition is coated on the electronic parts, and then the resultant film is baked. The outer electrode thus formed is then applied on the surface thereof with a copper plating or a nickel plating, after which the resultant electronic parts can be mounted on a printed wiring board by means of soldering. Since the polymer component is flexible, and the skeleton thereof is provided with rubber elasticity in this case also, the outer electrode material is excellent in stress relaxation and in reflow solderability, thereby making it possible to improve the durability of the electronic parts mounted on the printed wiring board. It is preferable that the outer electrode material is provided with the same properties as those of the aforementioned packaging material for wound coil.
In this case, instead of soldering the outer electrode, the aforementioned conductive material paste may be coated either on the aforementioned outer electrode or an outer electrode consisting of the conventional material, or on the soldering land of the printed wiring board, and then heated to form a cementing material for electronic parts. Heating condition in this case may be such that heating may be performed in the range of ordinary temperature to 160xc2x0 C. for several minutes to 20 minutes. Namely, the curing of this conductive material paste can be performed at a lower temperature as compared with the conventional soldering paste using a rosin-based material, thereby making it possible to minimize the damage to the other mounted parts on the printed wiring board, that might be caused due to the heating temperature.
Furthermore, when a cementing material to be obtained from an electronic composition comprising a resin material composition having the aforementioned features (a) and (b), or (a) to (c), or a powdery filler having the aforementioned features (d) and (e), or (d) to (f) is interposed between a green sheet laminate corresponding to an inductor portion and a green sheet laminate corresponding to a condenser portion of LC laminate composite electronic parts, it is possible, owing mainly to the low elastic modulus or flexibility of the polymer component, to relieve a stress that may be generated due to a difference in shrinkage factor between these green sheet laminates on the occasion of baking, thereby making it possible to prevent cracks from generating in the resultant baked body.
Further, when a green sheet laminate corresponding to an inductor portion and a green sheet laminate corresponding to a condenser portion are prepared in advance, and then bodies to be cemented and differing in expansion coefficient are bonded together by making use of an electronic material composition as in the case of the LC element which has been bonded by making use of an electronic material composition having the aforementioned features (d) and (e), or (d) to (f), it is possible to obtain electronic parts exhibiting relaxativity to a thermal stress even if the electronic parts are placed under a condition where temperature is differentiated.
Additionally, when the aforementioned magnetic material composition is employed as a caulking material for filling a joint portion of electromagnetic shielding board or tile constituting the external wall of building, it is possible to improve the heat resistance, weatheability and electromagnetic shielding effect of the joint portion without generating cracks owing to the low elastic modulus or flexibility of the polymer component even if the joint portion is exposed to a repeated difference in temperature of cold and hot. On this occasion, since the caulking material can be cured at the ordinary temperature, it is also convenient in this respect.
As explained above, the electronic material composition of this invention can be used for various end-use. For example, as mentioned above, the polymer component can be employed in a semi-cured state as in the cases of applying it for extrusion-molding the electromagnetic shielding layer of casing or for extrusion-molding the cover or skin of cable. However, in addition to these end-uses, the polymer component can be employed in a semi-cured state for other end-uses in the same manner as mentioned above. Namely, by controlling the heating temperature or heating time, it is possible to prevent electronic parts of electronic products from being damaged due to heating and to obtain other advantages.